A. Field of the Invention
The present invention relates to lighting fixtures that produce high intensity, controlled, and concentrated light beams for use at relatively distant targets. In particular, the invention relates to such lighting fixtures, their methods of use, and their use in systems where a plurality of such fixtures are used in combination, usually elevated on poles, to compositely illuminate a target area energy-efficiently, with reduced glare and spill light. One primary example is illumination of a sports field.
B. Problems in the Art
Illumination of sports fields is generally called sports lighting. FIGS. 1A–1G illustrate one such sports lighting configuration. Football field 5 of FIG. 1A is illuminated by a set of arrays 1 of light fixtures 2 elevated on poles 6 (see FIG. 1A). As is well known in the art, there are known methods to design the number, type, and position of poles 6 and fixtures 2 to provide a desired or required amount and uniformity of light for the field. There are usually pre-designed lighting quantity and uniformity specifications to follow.
In recent times, sports lighting has also had to deal with the issue of glare and spill light. For example, if light travels outside the area of the sports field, it can spill onto residential houses near the sports field. Also, the high intensity of the lamps can cause glare to such homeowner or create safety issues for drivers on nearby roads. Some communities have enacted laws regulating how much glare or spill light can be caused by sports lighting or other wide-area outdoors lighting. While a number of attempted remedies exist, many result in blocking, absorbing, or otherwise reducing the amount of light going to the field. This can not only increase cost of the lighting system because of the glare or spill control measures, but in some cases requires additional fixtures to meet minimum light quantity and uniformity specifications. More cost might therefore be incurred, to make up for the light lost in glare and spill control measures. In some cases, it can even require more costly and/or additional poles to support the additional fixtures. Arrays can be more quickly and efficiently erected on poles if at least partially factory pre-assembled and the fixtures are either pre-aimed or are aimable prior to elevating the pole. All that would remain is to ensure the rotational position of the pole is accurate. However, this is not a trivial task. What might otherwise be considered a small departure from the correct rotational position could mean a significant departure from the desired or planned uniformity and intensity of light on the target. It also could mean significant light is shifted or spilled outside the target, than if vertical plane of the array is correctly oriented to the target by the correct rotational position of the pole around its vertical axis.